Combinatorial Library Research Core The Combinatorial Library Research Core will focus on using several combinatorial library screening approaches to develop a series of peptide or oligonucleotide aptamers that display high affinity and high selectivity for certain cell surface receptors/proteins on tumor cells, endothelial cells, or proteins on subendothelial matrix, or intracellular proteins being addressed in different projects. The target proteins include the ccv|33 integrin, TVA receptor, and HER2 receptor for projects 1, 2, and 4, various signaling proteins for projects 5, 6 and certain integrins for project 6. We will use the library screening technology platforms that have been established at UNC-Chapel Hill, Duke University, and Argonne National Laboratory, including mRNA-display, phage-display, and yeast two-hybrid based technologies for selecting peptide aptamers and SELEX based technology for selecting nucleic acid aptamers. Various peptide or oligonucleotide libraries will be constructed and screened using different selection approaches. The specific aims of the core projects are: 1) Use mRNA-displayed 10FN3 domain library to select single domain antibody mimics that bind to avps integrin and TVA receptor; 2) Use phage-displayed combinatorial peptide libraries, FN3 or Top7 domain libraries, and Herceptin Fab antibody libraries to screen for HER2-binding or ccvpS-binding binding aptamers or Fab fragments; 3) Use a combination of yeast two-hybrid screening with phage-display to isolate scFvs that bind to the target signaling proteins of interest in the cytoplasm; 4) Use high complexity oligonucleotide libraries containing modified bases (2'- fluorine) to select RNA aptamers that bind to HER2 and to novel tumor cell markers. We will work with the Hahn lab to develop affinity-based signaling sensors to be used in projects 5 and 6. All the selected affinity molecules will be systematically optimized and characterized for target binding and specificity, and expressed or synthesized for applications. The availability of these novel affinity molecules for cellular and molecular recognition will play a vital role in the related projects. We will also make our efforts to facilitate the accessibility of these affinity reagents by other Centers of Cancer Nanotechnology Excellence.